Machines for cleaning wafers and disks in the electronics industry are generally well known. For example, semiconductor wafers, magnetic disks, and other workpieces often come in the form of flat, substantially planar, circular disks. In the manufacture of integrated circuits, semiconductor wafer disks are sliced from a silicon ingot and prepared for further processing. After each wafer is sliced from the ingot, it must be thoroughly cleaned, rinsed, and dried to remove debris from the surface of the wafer. Thereafter, a series of steps are performed on the wafer to build the integrated circuits on the wafer surface, including applying a layer of microelectronic structures and thereafter applying a dielectric layer. Often, the disks must be planarized upon the application of the dielectric layer. For a discussion of chemical mechanical planarization (CMP) processes and apparatus, see, for example, Arai, et al., U.S. Pat. No. 5,099,614, issued March, 1992; Karlsrud, U.S. Pat. No. 5,498,196, issued March, 1996; Arai, et al., U.S. Pat. No. 4,805,348, issued February, 1989; Karlsrud et al., U.S. Pat. No. 5,329,732, issued July, 1994; and Karlsrud et al., U.S. Pat. No. 5,498,199, issued March, 1996.
After each processing step, it is often desirable to thoroughly clean, rinse, and dry the workpiece to ensure that debris is removed from the workpiece. Thus, methods and apparatus for quickly and efficiently cleaning, rinsing, and drying wafers are needed which facilitate high workpiece throughput, while at the same time thoroughly cleaning and drying the wafers with a minimum of wafer breakage. For a discussion of existing wafer cleaning machines, see, for example, Lutz, U.S. Pat. No. 5,442,828, issued Aug. 22, 1995; Frank et al., U.S. Pat. No. 5,213,451, issued May 25, 1993; and Onodera, U.S. Pat. No. 5,357,645, issued Oct. 25, 1994.
Presently known wafer cleaning machines are unsatisfactory in several regards. For example, as the demand increases for semiconductor products, and in particular integrated circuit devices, the need for higher throughput wafer cleaning machines has correspondingly increased. However, the single input configuration of presently known wafer cleaning machines continues to impede throughput.
In addition, the pressure on wafer cleaning machine manufacturers to increase throughput has driven many manufacturers to design machines with high rotational spin rates (e.g., 1,800-2,200 RPM) to spin-dry the wafers very quickly. In so doing, the industry is currently experiencing an unacceptably high level of wafer breakage in the spin-dry operation. This breakage can be quite costly, particularly for wafers which comprise integrated circuits in the latter stages of processing.
A wafer cleaning machine is thus needed which overcomes the shortcomings of the prior art.